Impact of Preanalytical Factors on the Measurement of Tumor Tissue Biomarkers Using Immunohistochemistry

Impact of Prolonged Ischemia on the Immunohistochemical Expression of Programmed Death Ligand 1 (PD-L1)

Antibodies targeting programmed death receptor 1 or programmed death ligand 1 (PD-L1) have become a standard of care to treat different cancers; for some of these tumors, there is a correlation between tissue expression of PD-L1 and response rates in patients. Although most of the analytical challenges in the evaluation of PD-L1 expression have been standardized, preanalytical issues have been less explored. The objective of this study was to evaluate the impact of time of ischemia on the performance of 2 commonly used antibodies against PD-L1. Sixteen tonsillectomy samples were kept in ischemia for <30 minutes from sample obtention (control) and 1, 3, 6, 12, and 24 hours at room temperature before formalin fixation and paraffin embedding. Selected areas were inserted into TMA paraffin recipient blocks stained with SP142 and SP263 antibodies and evaluated by 2 blind observers. The proportion of suboptimally stained samples was significantly higher for samples with cold ischemia times 6 hours or over ( P <0.0001). False-negative results were 25% in samples exposed to 6 hours of ischemia and raised to 34% for samples remaining in ischemia for 12 or 24 hours. When all observations were pooled, SP142 provided suboptimal results in 24% of observations and SP263 in 12.5%; this is a statistically significant difference ( P =0.042). In conclusion, the quality of staining for PD-L1 in tonsil samples varies with the time of cold ischemia. The SP142 antibody presented a significantly lower tolerance to prolonged cold ischemia than SP263. These results reveal the relevance of controlled preanalytical processing of samples.

Immunohistochemical expression of P53 protein in nephroblastoma: a predictor of unfavorable prognosis

OBJECTIVE

Immunohistochemical expression of P53 protein is so closely related to status of mutation of P53 gene which is tightly linked with pathogenesis of nephroblastoma or Wilms tumor. This study aims to determine the immunohistochemical expression of P53 protein and its predictors in formalin-fixed paraffin-embedded tissue blocks of patients with nephroblastoma.

MATERIALS AND METHODS

A series of 83 histologically diagnosed cases of nephroblastoma from formalin-fixed paraffin-embedded tissue blocks archived at the Department of Pathology, Makerere University, in Kampala, Uganda, were analyzed. Monoclonal anti-p53 antibody (DO-7, DAKO) was used to assess the expression of P53 protein expression. Multivariable logistic regression analysis was performed to determine the predictors of P53 protein immunohistochemical expression, and statistical significance was considered when p-value was less than 0.05.

RESULTS

Most (42.2%, n = 35) of the cases were in advanced tumor stages (III-V), and almost one-quarter (21.7%, n = 18) of the cases were in high-risk group. The immunohistochemical expression of P53 protein was (8.4%, n = 7), and there were more (83.3%, n = 5) positive anaplastic cases for P53 protein compared with (2.6%, n = 2) of P53 expression for non-anaplastic cases. High risk (AOR = 3.42, 95% CI = 7.91-12.55, p = 0.037) and anaplasia (AOR = 1.41, 95% CI = 13.85-4.46, p = 0.001) were potential predictors of immunohistochemical expression of P53 protein.

CONCLUSION

Most of patients with nephroblastoma in resources-limited settings are diagnosed with advanced clinical stages. Association of P53 protein with anaplasia found in this study indicates the possibility of having novel target therapy for treatment of patients with anaplastic form of nephroblastoma with a focus of identifying molecules that lead to its suppression in such subpopulations of patients with nephroblastoma.

Assessment of the Impact of Alternative Fixatives on HER2 Detection in Breast Cancer and Gastric Cancer Tumor Specimens

The type of fixative used for preserving tumor specimens can significantly impact the performance of the immunohistochemistry and in situ hybridization assays used for assessing human epidermal growth factor receptor 2 (HER2) status. This study reports the prevalence of the use of alternative fixatives other than the guideline-recommended 10% neutral buffered formalin (NBF) during HER2 testing in a real-world setting. The effects of alternative fixatives [20% NBF and 10% unbuffered formalin (UBF) fixatives] on HER2 testing of breast cancer (BC) and gastric cancer (GC) cell lines and tissues are also assessed. Overall, 117,636 tumor samples received at a central laboratory from >8000 clinical trial sites across 60 countries were reviewed to determine the prevalence of alternative fixative usage. To investigate the impact of alternative fixatives, 27 cell lines (21 BC and 6 GC) and 76 tumor tissue samples (50 BC and 26 GC) were fixed in 10% NBF, 20% NBF, or 10% UBF, and evaluated for HER2 status by immunohistochemistry and in situ hybridization. Real-world data showed that 9195 (7.8%) tumor samples were preserved using an alternative fixative. In cell lines, overall percentage agreement, negative percentage agreement, and positive percentage agreement among the 3 fixatives were 100%. In tumor tissues, the agreement among 10% NBF, 20% NBF, and 10% UBF ranged between 94.7% and 96.6% for negative percentage agreement and 90.9% for overall percentage agreement compared with a range of 58.3% to 66.7% for positive percentage agreement. These results suggest that alternative fixatives may have the potential to convert HER2 status in tissues from positive to negative.

Considerations for Whole-Slide Analysis of Murine Xenografts Experiments

Histochemistry of tumor sections is a widely employed technique utilized to examine cell death in preclinical xenograft animal models of cancer. However, this is under the assumption that tumors are homogeneous, leading to practices such as automatic cell counting across the entire section. We have noted that in our experiments the core of the tumor is largely or partially necrotic, and lacks evidence of vascularization (in contrast to the outer areas of the tumor). We note that this can bias and confound immunohistochemical analyses that do not take care to sample areas of interest in a way to take this into account. Design-based stereology with image analysis techniques is an alternative process that could be used to measure the volume of the necrotic region compared to the volume of the whole tumor.